Regio- and Stereocontrolled Palladium- or Iridium-Catalyzed Allylation

We studied palladium- or iridium-catalyzed allylation as an effective method for the asymmetric synthesis of (alpha)-amino acids, hydroxylamines, oximes, and amines. The stereochemistry of the palladium-catalyzed allylic alkylation of a prochiral diphenylimino glycinate was controlled by chiral PTC, and gave chiral amino acids. In contrast, iridium-catalyzed allylic substitution of diphenylimino glycinate proceeded with good enantio- and diastereoselectivities with a new bidentate chiral ligand to give a novel method for preparing two branched diastereoisomers by simply switching the base. For the synthesis of (alpha),(alpha)-disubstituted amino acids, the palladium-catalyzed tandem reaction of dehydroamino acids was developed based on radical chemistry. Next, the viability of oximes and hydroxylamines as oxygen atom nucleophiles in transition metalcatalyzed allylic substitutions was examined. Regio- and enantioselective allylic substitution of oximes and hydroxylamines was achieved by using the iridium complex of chiral pybox ligand. Sequential allylic amination gave a novel method for preparing azacycles. Finally, umpolung allylation with aldehyde or imine was studied by using palladium catalyst and indium iodide. The palladium-indium iodide-mediated reaction of chiral 2-vinylaziridines with aldehydride proceeded with excellent diastereoselectivity. The role of water in directing the diastereo- or regioselectivities was investigated in the allylation and propargylation of chiral oxime ether. The allylation of oxime ether with monosubstituted allylic reagents afforded either (gamma)adduct or (alpha)-adduct depending on the reaction conditions.